A fastening system without an additional locking element is known from DE 199 29 896 A1. A characteristic feature of a fastening system of this kind is that the first and second retaining profiles used have very different geometries and that the joining methods of the different types of retaining profile differ greatly as a result. In particular, the second retaining profiles, which are designed as hook elements and joined to form a hook connection, involve a technical problem. While the familiar hook connection effectively prevents floor panels from being slid apart in the plane at right angles to the small faces of the connected panels, it does not afford satisfactory resistance to the hook elements being released in a direction perpendicular to the plane of the installed panels.
A fastening system of this kind is used with preference for so-called laminate flooring that displays a core made of a wood material, such as MDF, HDF or particleboard material. The mechanical retaining profiles are generally milled into the small faces of boards made of wood materials.
Laminate flooring is predominantly laid in floating fashion. To reduce footstep sound, a footstep sound-insulating intermediate layer is usually laid between the base surface and the laminate panels. It is also known for a footstep sound-insulating layer to be permanently attached to the underside of laminate panels that faces the base surface.
The hook connection of the known fastening system is particularly problematic if, in the region of a hook connection, only the panel whose hook element is at the bottom, i.e. facing the base surface, is exposed to a high load. The upper hook element of the adjacent panel, hooked into the bottom hook, is not exposed to loading, as a result of which the load only presses the panel with the hook element at the bottom into the generally soft footstep sound-insulating intermediate layer. The top hook element of the non-loaded panel releases itself from the bottom hook element of the adjacent panel in the process. The hook connection ceases to function, and the function usually cannot be restored.
According to the prior art, undercuts are integrated in the hook connection, by means of which releasing of the hook connection perpendicular to the installation plane of the panels is said to be prevented. These undercuts have, however, proven to be insufficient to afford this kind of fastening element sufficient strength.
A generic fastening system displaying an additional locking element in known from WO 01/51732 A1. Following interlocking of the hook elements, the locking element has to be subsequently inserted at the point of connection. This requires an additional work step. Moreover, fitting of the locking element causes problems if a row of panels is located very close in front of a wall. Insufficient space is then available for the locking element to be inserted at the point of connection.